Electrostatic puck assembly with metal bonded backing plate

ABSTRACT

An electrostatic puck assembly includes an upper puck plate, a lower puck plate and a backing plate. The upper puck plate comprises AlN or Al 2 O 3  and has a first coefficient of thermal expansion. The lower puck plate comprises a material having a second coefficient of thermal expansion that approximately matches the first coefficient of thermal expansion and is bonded to the upper puck plate by a first metal bond. The backing plate comprises AlN or Al 2 O 3  and is bonded to the lower puck plate by a second metal bond.

RELATED APPLICATIONS

This patent application is a continuation application of U.S. patentapplication Ser. No. 15/916,201, filed Mar. 8, 2018, which is acontinuation application of U.S. patent application Ser. No. 14/830,389,filed Aug. 19, 2015, which claims the benefit under 35 U.S.C. § 119(e)of U.S. Provisional Application No. 62/163,805, filed May 19, 2015, allof which are incorporated by reference herein.

TECHNICAL FIELD

Some embodiments of the present invention relate, in general, to asubstrate support assembly and electrostatic puck assembly that areusable for high temperature processes.

BACKGROUND

Electrostatic chucks are widely used to hold substrates, such assemiconductor wafers, during substrate processing in processing chambersused for various applications, such as physical vapor deposition,etching, or chemical vapor deposition. Electrostatic chucks typicallyinclude one or more electrodes embedded within a unitary chuck bodywhich includes a dielectric or semi-conductive ceramic material acrosswhich an electrostatic clamping field can be generated.

Electrostatic chucks offer several advantages over mechanical clampingdevices and vacuum chucks. For example, electrostatic chucks reducestress-induced cracks caused by mechanical clamping, allow larger areasof the substrate to be exposed for processing (Utile or no edgeexclusion), and can be used in low pressure or high vacuum environments.Additionally, the electrostatic chuck can hold the substrate moreuniformly to a chucking surface to allow a greater degree of controlover substrate temperature.

Various processes used in the fabrication of integrated circuits maycall for high temperatures and/or wide temperature ranges for substrateprocessing. However, electrostatic chucks in etch processes typicallyoperate in a temperature range of up to about 120° C. At temperaturesabove about 120° C., the components of many electrostatic chucks willbegin to fail due to various issues such as de-chucking, plasma erosionfrom corrosive chemistry, bond reliability, and so on.

SUMMARY

In one embodiment, an electrostatic puck assembly includes an upper puckplate, a lower puck plate and a backing plate. The upper puck plate iscomposed of AlN or Al₂O₃ and has a first coefficient of thermalexpansion. The lower puck plate is composed of a material having asecond coefficient of thermal expansion that approximately matches thefirst coefficient of thermal expansion and is bonded to the upper puckplate by a first metal bond. The lower puck plate may be composed of a)Molybdenum, b) a metal matrix composite of Si, SiC and Ti, or c) a SiCporous body infiltrated with an AlSi alloy in embodiments. The backingplate is composed of AlN or Al₂O₃ and is bonded to the lower puck plateby a second metal bond.

In one embodiment, a method of manufacturing an electrostatic puckassembly includes forming an upper puck plate of AlN or Al₂O₃. The upperpuck plate may have a first coefficient of thermal expansion and mayinclude one or more heating elements and one or more electrodes toelectrostatically secure a substrate. The method further includesbonding a lower puck plate to the upper puck plate with a first metalbond, the lower puck plate having a second coefficient of thermalexpansion that approximately matches the first coefficient of thermalexpansion. The method further includes bonding a backing platecomprising AlN or Al₂O₃ to the lower puck plate with a second metalbond.

In one embodiment, a substrate support assembly includes a multi-layerstack. The multi-layer stack may include an electrically insulativeupper puck plate, a lower puck plate bonded to the upper puck plate by afirst metal bond, and an electrically insulative backing plate bonded tothe lower puck plate by a second metal bond. The upper puck plate mayinclude one or more heating elements and one or more electrodes toelectrostatically secure a substrate. The lower puck plate may includemultiple features distributed over a bottom side of the lower puck platemultiple different distances from a center of the lower puck plate,wherein each of the plurality of features accommodates a fastener. Thesubstrate support assembly further includes a cooling plate coupled tothe multi-layer stack by fasteners. Each fastener may apply anapproximately equal fastening force to couple the cooling plate to themulti-layer stack, wherein the approximately equal fastening forcefacilitates uniform heat transfer between the cooling plate and themulti-layer stack.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, in the figures of the accompanyingdrawings in which like references indicate similar elements. It shouldbe noted that different references to “an” or “one” embodiment in thisdisclosure are not necessarily to the same embodiment, and suchreferences mean at least one.

FIG. 1 depicts a sectional side view of one embodiment of a processingchamber;

FIG. 2 depicts an exploded view of one embodiment of a substrate supportassembly;

FIG. 3 depicts a sectional top view of one embodiment of anelectrostatic puck assembly;

FIG. 4A depicts a sectional side view of one embodiment of a substratesupport assembly;

FIG. 4B depicts a perspective view of one embodiment of an electrostaticpuck assembly;

FIG. 5A depicts a sectional side view of an electrostatic puck assembly,in accordance with one embodiment;

FIG. 5B depicts a perspective view of one embodiment of an electrostaticpuck assembly that corresponds to the electrostatic puck assembly ofFIG. 5A;

FIG. 6A depicts a sectional side view of an electrostatic puck assembly,in accordance with one embodiment;

FIG. 6B depicts a perspective view of one embodiment of an electrostaticpuck assembly that corresponds to the electrostatic puck assembly ofFIG. 5A; and

FIG. 7 illustrates one embodiment of a process for manufacturing asubstrate support assembly.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention provide a substrate supportassembly and an electrostatic puck assembly capable of operating attemperatures of up to about 250° C. without incurring damage to thesubstrate support assembly. In one embodiment, an electrostatic puckassembly includes an electrically insulative upper puck plate bonded toa lower puck plate by a metal bond. The electrostatic puck assemblyfurther includes a backing plate bonded to the lower puck plate byanother metal bond. The metal bonds may be each be an aluminum bond, anAlSi alloy bond, or other metal bond. The upper puck plate includes oneor more heating elements and one or more electrodes to electrostaticallysecure a substrate. The lower puck plate may include multiple featuresdistributed over a bottom side of the lower puck plate at differentdistances from a center of the lower puck plate, where each of thefeatures accommodates a fastener. The backing plate may include holesthat provide access to the features in the lower puck plate. Theelectrostatic puck assembly is a component in a substrate supportassembly that further includes a cooling plate coupled to theelectrostatic puck assembly (e.g., by the fasteners). The fasteners mayeach apply an approximately equal fastening force to couple the coolingplate to the electrostatic puck assembly. This approximately equalfastening force facilitates uniform heat transfer between the coolingplate and the electrostatic puck assembly.

The upper puck plate may be composed of a dielectric such as AlN orAl₂O₃. The lower puck plate may be composed of a material that has acoefficient of thermal expansion that approximately matches thecoefficient of thermal expansion of the material (e.g., Al₂O₃ or AlN)for the upper puck plate. The backing plate may be composed of the samematerial as the upper puck plate. Absent the use of a backing plate, theupper puck plate and lower puck plate may bow or warp due to forcescaused by the bond between the upper puck plate and the lower puckplate. For example, the upper puck plate may have a convex bow of up to300 microns. The bow may cause the electrostatic puck assembly to crackand/or may impair an ability of the electrostatic puck assembly tosecurely hold (e.g., chuck) a substrate such as a wafer. Additionally,the bow may cause delamination of a metal bond that secures the upperpuck plate to the lower puck plate and may reduce an ability to create avacuum seal.

Bonding the backing plate to a bottom of the lower puck plate may causean approximately equal force to be applied to a top and bottom of thebacking plate. By equalizing the forces on the top and bottom of thebacking plate, a bow in the electrostatic puck assembly including theupper puck plate and the lower puck plate may be nearly eliminated. Forexample, a bow in the electrostatic puck assembly may be reduced fromabout 0.3 mm to less than 0.1 mm (e.g., about 0.05 mm or 50 microns orless in embodiments). The reduction in the bow of the electrostatic puckassembly may improve an ability of the electrostatic puck assembly tosecure substrates, may reduce or eliminate cracking, may improve a sealbetween the upper puck plate and a supported substrate and may improve avacuum seal of the electrostatic puck assembly. In one embodiment, theforces (internal stress) on the upper puck plate are about −98+/−7Megapascals (MPa), the forces on the backing plate are about −136+/−5MPa, the forces on the top face of the lower puck plate are about 80 MPaand the forces on the bottom face of the lower puck plate are about 54MPa. A positive value represents a compressive force and a negativevalue represents a tensile force.

FIG. 1 is a sectional view of one embodiment of a semiconductorprocessing chamber 100 having a multi-layer electrostatic puck assembly150 disposed therein. The processing chamber 100 includes a chamber body102 and a lid 104 that enclose an interior volume 106. The chamber body102 may be fabricated from aluminum, stainless steel or other suitablematerial. The chamber body 102 generally includes sidewalls 108 and abottom 110. An outer liner 116 may be disposed adjacent the side walls108 to protect the chamber body 102. The outer liner 116 may befabricated and/or coated with a plasma or halogen-containing gasresistant material. In one embodiment, the outer liner 116 is fabricatedfrom aluminum oxide. In another embodiment, the outer liner 116 isfabricated from or coated with yttria, yttrium alloy or an oxidethereof.

An exhaust port 126 may be defined in the chamber body 102, and maycouple the interior volume 106 to a pump system 128. The pump system 128may include one or more pumps and throttle valves utilized to evacuateand regulate the pressure of the interior volume 106 of the processingchamber 100.

The lid 104 may be supported on the sidewall 108 of the chamber body102. The lid 104 may be opened to allow access to the interior volume106 of the processing chamber 100, and may provide a seal for theprocessing chamber 100 while closed. A gas panel 158 may be coupled tothe processing chamber 100 to provide process and/or cleaning gases tothe interior volume 106 through a gas distribution assembly 130 that ispart of the lid 104. Examples of processing gases that may be used toprocess substrates in the processing chamber include halogen-containinggas, such as C₂F₆, SF₆, SiCl₄, HBr, NF₃, CF₄, CHF₃, CH₂F₃, Cl₂ and SiF₄,among others, and other gases such as O₂ or N₂O. Examples of carriergases include N₂, He, Ar, and other gases inert to process gases (e.g.,non-reactive gases). The gas distribution assembly 130 may have multipleapertures 132 on the downstream surface of the gas distribution assembly130 to direct the gas flow to the surface of a substrate 144.Additionally, the gas distribution assembly 130 can have a center holewhere gases are fed through a ceramic gas nozzle. The gas distributionassembly 130 may be fabricated and/or coated by a ceramic material, suchas silicon carbide, Yttrium oxide, etc. to provide resistance tohalogen-containing chemistries to prevent the gas distribution assembly130 from corrosion.

An inner liner 118 may be coated on the periphery of a substrate supportassembly 148. The inner liner 118 may be a halogen-containing gas resistmaterial such as those discussed with reference to the outer liner 116.In one embodiment, the inner liner 118 may be fabricated from the samematerials of the outer liner 116.

The substrate support assembly 148 is disposed in the interior volume106 of the processing chamber 100 below the gas distribution assembly130. The substrate support assembly 148 includes the electrostatic puckassembly 150 (also referred to as an electrostatic puck or multilayerstack). The electrostatic puck assembly 150 holds the substrate 144during processing. The electrostatic puck assembly 150 described inembodiments may be used for Johnsen-Rahbek and/or Coulombicelectrostatic chucking.

The electrostatic puck assembly 150 includes an upper puck plate 192, alower puck plate 190 and a backing plate 196. The upper puck plate 192may be bonded to the lower puck plate 190 by a first metal bond, and thelower puck plate 190 may be bonded to the backing plate 196 by a secondmetal bond. The upper puck plate 192 may be a dielectric or electricallyinsulative material that is usable for semiconductor processes attemperatures of 200° C. and above. In one embodiment, the upper puckplate 192 is composed of materials usable from about 20° C. to about500° C. In one embodiment, the upper puck plate 192 is AlN or Al₂O₃.

The lower puck plate 190 may have a coefficient of thermal expansionthat is matched (or approximately matched) to a coefficient of thermalexpansion of the upper puck plate 192 and/or backing plate 196. In oneembodiment, the lower puck plate 190 is a SiC porous body that isinfiltrated with an AlSi alloy (referred to as AlSiSiC). The AlSiSiCmaterial may be used, for example, in reactive etch environments. Inanother embodiment, the lower puck plate 190 is a metal matrix compositeof Si, SiC and Ti (SiSiCTi). Alternatively, the lower puck plate 190 maybe Molybdenum. AN may have a coefficient of thermal expansion of about4.5-5 parts per million per degrees C. (ppm/° C.). AlSiSiC may have acoefficient of thermal expansion of around 5 ppm/° C. Molybdenum mayhave a coefficient of thermal expansion of about 5.5 ppm/° C.Accordingly, in one embodiment, the upper puck plate 192 and backingplate 196 are AlN and the lower puck plate 190 is Molybdenum or AlSiSiC.A metal matrix composite of SiSiCTi may have a coefficient of thermalexpansion of about 8 ppm/° C. Al₂O₃ may have a coefficient of thermalexpansion of about 8 ppm/° C. Accordingly, in one embodiment having anAl₂O₃ upper puck plate, an SiSiCTi lower puck plate, and an Al₂O₃backing plate, the coefficient of thermal expansion for the lower puckplate 190, the upper puck plate 192 and the backing plate 196 may all beabout 8 ppm/° C.

In one embodiment, the upper puck plate 192 is coated with a protectivelayer 136, which may be a plasma resistant ceramic coating. Theprotective layer 136 may also coat a vertical wall of the upper puckplate 192, a metal bond between the upper puck plate 192 and lower puckplate 190, the backing plate 196, and/or the metal bond between thelower puck plate 192 and the backing plate 196. The protective layer 136may be a bulk ceramic (e.g., a ceramic wafer), a plasma sprayed coating,a coating deposited by ion assisted deposition (IAD), or a coatingdeposited using other deposition techniques. The protective layer 136may be Y₂O₃ (yttria or yttrium oxide), Y₄Al₂O₉ (YAM), Al₂O₃ (alumina)Y₃Al₅O₁₂ (YAG), YAlO₃ (YAP), Quartz, SiC (silicon carbide) Si₃N₄(silicon nitride) Sialon, (aluminum nitride), AlON (aluminumoxynitride), TiO₂ (titania), ZrO₂ (zirconia), TiC (titanium carbide),ZrC (zirconium carbide), TiN (titanium nitride), TiCN (titanium carbonnitride) Y₂O₃ stabilized ZrO₂ (YSZ), and so on. The protective layer mayalso be a ceramic composite such as Y₃Al₅O₁₂ distributed in Al₂O₃matrix, Y₂O₃—ZrO₂ solid solution or a SiC-Si₃N₄ solid solution. Theprotective layer may also be a ceramic composite that includes a yttriumoxide (also known as yttria and Y₂O₃) containing solid solution. Forexample, the protective layer may be a ceramic composite that iscomposed of a compound Y₄Al₂O₉ (YAM) and a solid solutionY_(2-X)Zr_(x)O₃ (Y₂O₃—ZrO₂ solid solution). Note that pure yttrium oxideas well as yttrium oxide containing solid solutions may be doped withone or more of ZrO₂, Al₂O₃, SiO₂, B₂O₃, Er₂O₃, Nd₂O₃, Nb₂O₅, CeO₂,Sm₂O₃, Yb₂O₃, or other oxides. Also note that pure Aluminum Nitride aswell as doped Aluminum Nitride with one or more of ZrO₂, Al₂O₃, SiO₂,B₂O₃, Er₂O₃, Nd₂O₃, Nb₂O₅, CeO₂, Sm₂O₃, Yb₂O₃, or other oxides may beused. Alternatively, the protective layer may be sapphire or MgAlON.

The substrate support assembly 148 further includes a cooling plate 164,which is coupled to the backing plate 196. The cooling plate 164 is athermally conductive base that may act as a heat sink. In oneembodiment, the cooling plate 164 is coupled to the electrostatic puckassembly 150 by multiple fasteners. In one embodiment, the substratesupport assembly 148 additionally includes a mounting plate 162 and apedestal 152.

The mounting plate 162 is coupled to the bottom 110 of the chamber body102 and includes passages for routing utilities (e.g., fluids, powerlines, sensor leads, etc.) to the cooling plate 164 and theelectrostatic puck assembly 150. The cooling plate 164 and/orelectrostatic puck assembly 150 may include one or more optionalembedded heating elements 176, optional embedded thermal isolators 174and/or optional conduits 168, 170 to control a lateral temperatureprofile of the substrate support assembly 148.

The conduits 168, 170 may be fluidly coupled to a fluid source 172 thatcirculates a temperature regulating fluid through the conduits 168, 170.The embedded thermal isolators 174 may be disposed between the conduits168, 170 in one embodiment. The embedded heating elements 176 areregulated by a heater power source 178. The conduits 168, 170 andembedded heating elements 176 may be utilized to control the temperatureof the electrostatic puck assembly 150, thereby heating and/or coolingthe electrostatic puck assembly 150 and the substrate 144 (e.g., awafer) being processed.

In one embodiment, the electrostatic puck assembly 150 includes twoseparate heating zones that can maintain distinct temperatures. Inanother embodiment, the electrostatic puck assembly 150 includes fourdifferent heating zones that can maintain distinct temperatures. Othernumbers of heating zones may also be used. The temperature of theelectrostatic puck assembly 150 and the cooling plate 164 may bemonitored using one or more temperature sensors 138, which may bemonitored using a controller 195. Embodiments enable the electrostaticpuck assembly 150 to maintain temperatures of up to about 250° C. whilethe cooling base maintains a temperature of about 60° C. Accordingly,embodiments enable a temperature delta of up to about 190° C. to bemaintained between the electrostatic puck assembly 150 and the coolingplate 164.

The electrostatic puck assembly 150 may further include multiple gaspassages such as grooves, mesas and other surface features, that may beformed in an upper surface of the upper puck plate 192. The gas passagesmay be fluidly coupled to a source of a heat transfer (or backside) gassuch as He via holes drilled in the upper puck plate 192. In operation,the backside gas may be provided at controlled pressure into the gaspassages to enhance the heat transfer between the upper puck plate 192and the substrate 144.

In one embodiment, the upper puck plate 192 includes at least oneclamping electrode 180 controlled by a chucking power source 182. Theclamping electrode 180 (also referred to as a chucking electrode) mayfurther be coupled to one or more RF power sources 184, 186 through amatching circuit 188 for maintaining a plasma formed from process and/orother gases within the processing chamber 100. The one or more RF powersources 184, 186 are generally capable of producing an RF signal havinga frequency from about 50 kHz to about 3 GHz and a power of up to about10,000 Watts. In one embodiment, an RF signal is applied to the metalbase, an alternating current (AC) is applied to the heater and a directcurrent (DC) is applied to the clamping electrode 180.

FIG. 2 depicts an exploded view of one embodiment of the substratesupport assembly 148, including the electrostatic puck assembly 150, thecooling plate 164 and the pedestal 152. The electrostatic puck assembly150 includes the upper puck plate 192, as well as the lower puck plate(not shown) and the backing plate (not shown). As shown, an o-ring 240may be disposed on the cooling plate 164 along a perimeter of a top sideof the cooling plate 164. In one embodiment, the o-ring 240 isvulcanized to the cooling plate 240. Alternatively, the o-ring 240 maybe disposed on the top side of the cooling plate 164 without beingvulcanized thereto.

In one embodiment, the o-ring 240 is a perfluoropolymer (PFP) o-ring.Alternatively, other types of high temperature o-rings may be used. Forexample, the o-ring 240 may be a polyimide ring such as a Cirlex® ringor a Kapton® ring. In one embodiment, thermally insulating hightemperature o-rings are used. The o-ring 240 may be a stepped o-ringhaving a first step at a first thickness and a second step at a secondthickness. This may facilitate uniform tightening of fasteners 292 bycausing the amount of force used to tighten the fasteners 292 toincrease dramatically after a set amount of compression of the PFPo-ring 240.

Additional o-rings (not shown) may also be attached to the top side ofthe cooling plate around a hole 280 at a center of the cooling plate 164through which cables are run. Other smaller o-rings may also be attachedto the cooling plate 164 around other openings, around lift pins, and soforth. Alternatively, or additionally, a gasket (e.g., a PFP gasket) maybe attached to the top side of the cooling plate 164. Examples of PFPsusable for the gasket or o-ring 240 are Dupont's™ ECCtreme™, Dupont'sKALREZ® (e.g., KALREZ 8900) and Daikin's® DUPRA™. The o-ring 240 orgasket provide a vacuum seal between a chamber interior volume andinterior volumes within the electrostatic puck assembly 150. Theinterior volumes within the electrostatic puck assembly 150 include openspaces within the pedestal 152 for routing conduits and wiring.

In one embodiment, the cooling plate 164 additionally includes numerousfeatures 242 through which fasteners 292 are inserted. If a gasket isused, the gasket may have cutouts at each of the features 242. Fasteners292 may extend through each of the features 242 and attach to additionalportions of the fasteners (or additional fasteners) that are insertedinto additional features formed in the lower puck plate. For example, abolt may extend through a feature 242 in the cooling plate 164 and bescrewed into a nut disposed in a feature of the lower puck plate. Eachfeature 242 in the cooling plate 164 may line up to a similar feature(not shown) in the lower puck plate.

The upper puck plate 192 has a disc-like shape having an annularperiphery that may substantially match the shape and size of a substratepositioned thereon. An upper surface of the upper puck plate 192 mayhave an outer ring 216, multiple mesas 210 and channels 208, 212 betweenthe mesas 210. The upper puck plate 192 may also have additionalfeatures such as step 193. In one embodiment, the upper puck plate 192may be fabricated by an electrically insulative ceramic material.Suitable examples of the ceramic materials include aluminum nitride(AlN), aluminum oxide (Al₂O₃), and the like.

The cooling plate 164 attached below the electrostatic puck assembly 150may have a disc-like main portion 224 and an annular flange extendingoutwardly from the main portion 224 and positioned on the pedestal 152.In one embodiment, the cooling plate 164 may be fabricated by a metal,such as aluminum or stainless steel or other suitable materials.Alternatively, the cooling plate 164 may be fabricated by a compositeceramic, such as an aluminum-silicon alloy infiltrated SiC or Molybdenumto match a thermal expansion coefficient of the electrostatic puckassembly 150. The cooling plate 164 should provide good strength anddurability as well as heat transfer properties.

FIG. 3 depicts a top view of one embodiment of a lower puck plate 300used in an electrostatic puck assembly. Lower puck plate 300 maycorrespond to lower puck plate 190, or any other lower puck platedescribed herein. As shown, the lower puck plate 300 has a radius R3,which may be substantially similar to a radius of substrates or wafersthat are to be supported by the electrostatic puck assembly. The lowerpuck plate 300 additionally includes multiple features 305. The featuresmay match similar features in a cooling plate to which an electrostaticpuck assembly including the lower puck plate 300 is mounted. Eachfeature 305 accommodates a fastener. For example, a bolt (e.g., astainless steel bolt, galvanized steel bolt, etc.) may be placed intoeach feature such that a head of the bolt is inside of an opening largeenough to accommodate the head and a shaft of the bolt extends out of abottom side of the lower puck plate 300. The bolt may be tightened ontoa nut that is placed in a corresponding feature in the cooling plate.Alternatively, features 305 may be sized to accommodate a nut, and mayinclude a hole that can receive a shaft of a bolt that is accommodatedby a corresponding feature in the cooling plate. In another example, ahelical insert (e.g., a Heli-Coil®) or other threaded insert (e.g., apress fit insert, a mold-in insert, a captive nut, etc.) may be insertedinto one or more of the features to add a threaded hole thereto. A boltplaced inside of the cooling plate and protruding from the cooling platemay then be threaded into the threaded insert to secure the coolingplate to the puck. Alternatively, threaded inserts may be used in thecooling plate.

The features 305 may be slightly oversized as compared to a size of thefasteners to accommodate a greater coefficient of thermal expansion ofthe fasteners. In one embodiment, the fasteners are sized such that thefasteners will not exert a force on the features when the fasteners areheated to 500 or 600 degrees Celsius.

As shown, multiple sets of features 305 may be included in the lowerpuck plate 300. Each set of features 305 may be evenly spaced at aparticular radius or distance from a center of the lower puck plate. Forexample, as shown a first set of features 305 is located at a radius R1and a second set of features 305 is located at a radius R2. Additionalsets of features may also be located at additional radiuses.

In one embodiment, the features are arranged to create a uniform load onthe electrostatic puck assembly including the lower puck plate 300. Inone embodiment, the features are arranged such that a bolt is locatedapproximately every 30-70 square centimeters (e.g., every 50 squarecentimeters). In one embodiment, three sets of features are used for a12 inch diameter electrostatic puck assembly. A first set of featuresmay be located about 4 inches from a center of the lower puck plate 300and includes about 4 features. A second set of features may be locatedabout 6 inches from a center of the lower puck plate 300 and includesabout 6 features. A third set of features may be located about 8 inchesfrom a center of the lower puck plate 300 and includes about 8 features.Alternatively, two sets of features may be used. In one embodiment, thelower puck plate 300 includes about 8-24 features arranged in sets at2-3 different radiuses, where each feature accommodates a fastener.

FIG. 4A depicts a sectional side view of one embodiment of a substratesupport assembly 405. The substrate support assembly 405 includes anelectrostatic puck assembly 410 made up of an upper puck plate 415, alower puck plate 420 and a backing plate 425 that may be bonded togetherby metal bonds. In one embodiment, the upper puck plate 415 is bonded tothe lower puck plate 420 by a first metal bond 450 and the lower puckplate 420 is bonded to the backing plate 425 by a second metal bond 455.In one embodiment, diffusion bonding is used as the method of metalbonding. However, other bonding methods may also be used to produce themetal bonds.

The upper puck plate 415 is composed of an electrically insulative(dielectric) ceramic such as AlN or Al₂O₃. In one embodiment, thebacking plate 425 is composed of the same material as the upper puckplate 415. This may cause approximately matching but opposite forces onthe lower puck plate 420 by the upper puck plate 415 and the backingplate 425. The approximately matching forces may minimize or eliminatebowing and cracking of the upper puck plate 415.

The upper puck plate 415 includes clamping electrodes 427 and one ormore heating elements 429. The clamping electrodes 427 may be coupled toa chucking power source (not shown), and to an RF plasma power supply(not shown) and an RF bias power supply (not shown) a matching circuit(not shown). The heating elements 429 are electrically connected to aheater power source (not shown) for heating the upper puck plate 415.

The upper puck plate 415 may have a thickness of about 3-10 mm. In oneembodiment, the upper puck plate 415 has a thickness of about 3-5 mm.The clamping electrodes 427 may be located about 0.3 to 1 mm from anupper surface of the upper puck plate 415, and the heating elements 429may be located about 2 mm under the clamping electrodes 427. The heatingelements 429 may be screen printed heating elements having a thicknessof about 10-200 microns. Alternatively, the heating elements 429 may beresistive coils that use about 1-3 mm of thickness of the upper puckplate 415. In such an embodiment, the upper puck plate 415 may have aminimum thickness of about 5 mm.

In one embodiment, the backing plate 425 has a thickness that isapproximately equal to the thickness of the upper puck plate 415. Forexample, the upper puck plate 415 and the backing plate 425 may eachhave a thickness of about 3-5 mm in an embodiment. In one embodiment,the backing plate 425 has a thickness of about 3-10 mm.

In one embodiment, the lower puck plate 420 has a thickness that isequal to or greater than the thickness of the upper puck plate 415 andthe backing plate 425. In one embodiment, the lower puck plate 420 has athickness of about 8-25 mm. In one embodiment, the lower puck plate 420has a thickness that is about 30%-330% greater than the thickness of theupper puck plate 415.

In one embodiment, the material used for the lower puck plate 420 may besuitably chosen so that a coefficient of thermal expansion (CTE) for thelower puck plate 420 material substantially matches the CTE of theelectrically insulative upper puck plate 415 material in order tominimize CTE mismatch and avoid thermo-mechanical stresses which maydamage the electrostatic puck assembly 410 during thermal cycling.

In one embodiment, the lower puck plate 420 is Molybdenum. Molybdenummay be used for the lower puck plate 420, for example, if theelectrostatic puck assembly 410 is to be used in an inert environment.Examples of inert environments include environments in which inert gasessuch as Ar, O2, N, etc. are flowed. Molybdenum may be used, for example,if the electrostatic puck assembly 410 is to chuck a substrate for metaldeposition. Molybdenum may also be used for the lower puck plate 420 forapplications in a corrosive environment (e.g., etch applications). Insuch an embodiment, exposed surfaces of the lower puck plate 420 may becoated with a plasma resistant coating after the lower puck plate 420 isbonded to the upper puck plate 415. The plasma coating may be performedvia a plasma spray process. The plasma resistant coating may cover, forexample, side walls of the lower puck plate and an exposed horizontalstep of the lower puck plate 420. In one embodiment, the plasmaresistant coating is Al₂O₃. Alternatively, the plasma resistant coatingmay be any of the materials described with reference to protective layer136 above.

In one embodiment, an electrically conductive metal matrix composite(MMC) material is used for the lower puck plate 420. The MMC materialincludes a metal matrix and a reinforcing material which is embedded anddispersed throughout the matrix. The metal matrix may include a singlemetal or two or more metals or metal alloys. Metals which may be usedinclude but are not limited to aluminum (Al), magnesium (Mg), titanium(Ti), cobalt (Co), cobalt-nickel alloy (CoNi), nickel (Ni), chromium(Cr), or various combinations thereof. The reinforcing material may beselected to provide the desired structural strength for the MMC, and mayalso be selected to provide desired values for other properties of theMMC, such as thermal conductivity and CTE, for example. Examples ofreinforcing materials which may be used include silicon (Si), carbon(C), or silicon carbide (SiC), but other materials may also be used.

The MMC material for the lower puck plate 420 is preferably chosen toprovide a desired electrical conductivity and to substantially match theCTE of the upper puck plate 415 material over the operating temperaturerange for the electrostatic puck assembly 410. In one embodiment, thetemperature may range from about 20° Celsius to about 500° Celsius. Inone embodiment, matching the CTEs is based on selecting the MCC materialso that the MCC material includes at least one material which is alsoused in the upper puck plate 415 material. In one embodiment, the upperpuck plate 415 includes AlN. In one embodiment, the MMC materialincludes a SiC porous body that is infiltrated with an AlSi alloy(referred to herein as AlSiSiC).

The constituent materials and composition percentages of the MMC may beselected to provide an engineered material which meets desirable designobjectives. For example, by suitably selecting the MCC material toclosely match the CTEs of the lower puck plate 420 and upper puck plate415, the thereto-mechanical stresses at an interface between the lowerpuck plate 420 and the upper puck plate 415 are reduced.

By matching coefficients of thermal expansion between the layers of theelectrostatic puck assembly 410, stress caused by bonding the lower puckplate 420 to the upper puck plate 415 and the backing plate 425 may beminimized. In one embodiment, the lower puck plate 420 is composed of ametal matrix composite material as described above. Alternatively, thelower puck plate 420 may be SiSiCTi or Molybdenum.

In one embodiment, the lower puck plate 420 has a roughened outer wallthat has been coated with a plasma resistant ceramic coating (notshown). Plasma resistant ceramic coatings are discussed in greaterdetail below with reference to FIGS. 5A-5B.

In one embodiment, the upper puck plate 415, the lower puck plate 420and the backing plate 425 comprise materials which include aluminum. Forexample, the upper puck plate 415 and backing plate 425 may each becomposed of Al₂O₃ or AlN and the lower puck plate 420 may be composed ofAlSiSiC.

Metal bond 450 may include an “interlayer” of aluminum foil that isplaced in a bonding region between the upper puck plate 415 and thelower puck plate 420. Similarly metal bond 455 may include an interlayerof aluminum foil that is placed in a bonding region between the lowerpuck plate 420 and the backing plate 425. Pressure and heat may beapplied to form a diffusion bond between the aluminum foil and the upperpuck plate 415 and between the aluminum foil and lower puck plate 420.Similarly, pressure and heat may be applied to form a diffusion bondbetween the aluminum foil and the lower puck plate 420 and between thealuminum foil and the backing plate 425. In other embodiments, thediffusion bonds may be formed using other interlayer materials which areselected based upon the materials used for upper puck plate 415, thelower puck plate 420 and the backing plate 425. In one embodiment, themetal bonds 455, 465 have a thickness of about 0.2-0.3 mm.

In one embodiment, the upper puck plate 415 may be directly bonded tothe lower puck plate 420 using direct diffusion bonding in which nointerlayer is used to form the bond. Similarly, the lower puck plate 420may be directly bonded to the backing plate 425 using direct diffusionbonding.

The upper puck plate 415 may have a diameter that is larger than adiameter of the lower puck plate 420 and the backing plate 425. In oneembodiment, the upper puck plate 415 and the lower puck plate 420 eachhas a diameter of about 300 mm and the backing plate 425 has a diameterof about 250 mm. In one embodiment, the backing plate 425 has a diameterthat is approximately 75-85% of the diameter of the upper puck plate415. An edge of a base plate 495 may have a similar diameter to thediameter of the upper puck plate 415. A plasma resistant and hightemperature o-ring 445 may be disposed between upper puck plate 415 andthe base plate 495. This o-ring 445 may provide a vacuum seal between aninterior of the substrate support assembly and a processing chamber. Theo-ring 445 may be made of a perfluoropolymer (PFP). In one embodiment,the o-ring 445 is a PFP with inorganic adders such as SiC. The o-ring445 may be replaceable. When the o-ring 445 degrades it may be removedand a new o-ring may be stretched over the upper puck plate 415 andplaced at a perimeter of the upper puck plate 415 at an interfacebetween the upper puck plate 415 and the base plate 495. The o-ring 445may protect the metal bonds 450, 455 from erosion by plasma.

The backing plate 425 is coupled to and in thermal communication with acooling plate 436 having one or more conduits 435 (also referred toherein as cooling channels) in fluid communication with a fluid source(not shown). The lower puck plate 420 and/or backing plate 425 mayinclude numerous features (not shown) for receiving fasteners. In oneembodiment, the cooling plate 436 and/or base plate 495 are coupled tothe electrostatic puck assembly 410 by multiple fasteners (not shown).The fasteners may be threaded fasteners such as nut and bolt pairs. Thelower puck plate 420 may include multiple features (not shown) foraccommodating the fasteners. The cooling plate 436 may likewise includemultiple features (not shown) for accommodating the fasteners.Additionally, the base plate 495 may include multiple features (notshown) for accommodating the fasteners. In one embodiment, the featuresare bolt holes with counter bores. The features may be through featuresthat extend through the lower puck plate 420 and backing plate 425.Alternatively, the features may not be through features. In oneembodiment, the features are slots that accommodate a t-shaped bolt heador rectangular nut that may be inserted into the slot and then rotated90 degrees. In one embodiment, the fasteners include washers, graphoil,aluminum foil, or other load spreading materials to distribute forcesfrom a head of the fastener evenly over a feature.

The cooling plate 436 may act as a heat sink to absorb heat from theelectrostatic puck assembly 410. In one embodiment (as shown), a lowthermal conductivity gasket 465 is disposed on the cooling plate 436.The low thermal conductivity gasket 465 may be, for example, a PFPgasket that is vulcanized to (or otherwise disposed on) the coolingplate 436. In one embodiment, the low thermal conductivity gasket has athermal conductivity of about 0.2 Watts per meter Kelvin (W/(m·K)) orlower. The fasteners may be tightened with approximately the same forceto evenly compress the low thermal conductivity gasket 465. The lowthermal conductivity gasket 465 may decrease heat transfer and act as athermal choke.

In one embodiment, a graphoil layer (not shown) is disposed over the lowthermal conductivity gasket 465. The graphoil may have a thickness ofabout 10-40 mil. The fasteners may be tightened to compress the graphoillayer as well as the low thermal conductivity gasket 465. The graphoilmay be thermally conductive.

In one embodiment, one or more PFP O-rings (not shown) may be disposedat an outer perimeter and/or an inner perimeter of the cooling plate164. The PFP o-ring(s) may be used instead of or in addition to the lowthermal conductivity gasket 465. The fasteners may all be tightened withapproximately the same force to compress the PFP o-ring(s) and cause aseparation (e.g., a gap) between the backing plate 425 of theelectrostatic puck assembly 410 and the cooling plate 436. Theseparation may be approximately the same (uniform) throughout theinterface between the backing plate 425 and the cooling plate 436. Thisensures that the heat transfer properties between the cooling plate 436and the backing plate 425 are uniform. In one embodiment the separationis about 2-10 mils. The separation may be 2-10 mils, for example, if thePFP o-ring is used without a graphoil layer. If a graphoil layer (orother gasket) is used along with the PFP o-ring, then the separation maybe about 10-40 mils. Larger separation may decrease heat transfer, andcause the interface between the backing plate 425 and the cooling plate436 to act as a thermal choke. The separation between the electrostaticpuck assembly 410 and the cooling plate 436 may minimize the contactarea between the electrostatic puck assembly 410 and the cooling plate436. In one embodiment, a conductive gas may be flowed into theseparation to improve heat transfer between the electrostatic puckassembly 410 and the cooling plate 436.

By maintaining a thermal choke between the electrostatic puck assembly410 and the cooling plate 436, the electrostatic puck assembly 410 maybe maintained at much greater temperatures than the cooling plate 436.For example, in some embodiments the electrostatic puck assembly 410 maybe heated to temperatures of 200-300 degrees Celsius, while the coolingplate 436 may maintain a temperature of below about 120 degrees Celsius.In one embodiment, the electrostatic puck assembly 410 may be heated upto a temperature of about 250° C. while maintaining the cooling plate436 at a temperature of about 60° C. or below. Accordingly, up to a 190°C. may be maintained between the electrostatic puck assembly 410 and thecooling plate 436 in embodiments. The electrostatic puck assembly 410and the cooling plate 436 are free to expand or contract independentlyduring thermal cycling.

The PFP gasket 465 and/or a separation between the backing plate 425 andthe cooling plate 436 may function as a thermal choke by restricting theheat conduction path from the heated electrostatic puck assembly 410 tothe cooled cooling plate 436. In a vacuum environment, heat transfer maybe primarily a radiative process unless a conduction medium is provided.Since the electrostatic puck assembly 410 may be disposed in a vacuumenvironment during substrate processing, heat generated by heatingelements 429 may be transferred more inefficiently across theseparation. Therefore, by adjusting the separation and/or other factorsthat affect heat transfer, the heat flux flowing from the electrostaticpuck assembly 410 to the cooling plate 436 may be controlled. To provideefficient heating of the substrate, it may be desirable to limit theamount of heat conducted away from the upper puck plate 415.

In one embodiment, the cooling plate 436 is coupled to the base plate495 by one or more springs 470. In one embodiment, the springs 470 arecoil springs. The springs 470 apply a force to press the cooling plate436 against the electrostatic puck assembly 410. A surface of thecooling plate 436 may have a predetermined roughness and/or surfacefeatures (e.g., mesas) that affect heat transfer properties between theelectrostatic puck assembly 410 and the cooling plate 436. Additionally,the material of the cooling plate 436 may affect the heat transferproperties. For example, an aluminum cooling plate 436 will transferheat better than a stainless steel cooling plate 436.

In some embodiments it may be desirable to provide an F signal throughthe electrostatic puck assembly 410 and to a supported substrate duringprocessing. In one embodiment, to facilitate the transmission of such anRF signal through the electrostatic puck assembly 410, an RF gasket 490is disposed on the base plate 495. The RF gasket 490 may electricallyconnect the base plate 495 to the lower puck plate 420, thus providing aconductive path past the backing plate 425. Due to the position of theRF gasket 490, a diameter of the backing plate 425 may be smaller than adiameter of the lower puck plate 420 and a diameter of the upper puckplate 415.

In one embodiment, a thermal spacer 485 is disposed adjacent to the RFgasket 490. The thermal spacer 485 may be used to ensure that the baseplate 295 will not come into contact with the lower puck plate 420. Inone embodiment, an o-ring 480 is disposed adjacent to the thermal spacer485. The o-ring 480 may be a PFP o-ring in one embodiment. The o-ring480 may be used to facilitate a vacuum seal. In one embodiment, amounting plate 440 is disposed beneath and coupled to the base plate495.

FIG. 4B depicts a perspective view of one embodiment of a bottom ofelectrostatic puck assembly 410 shown in FIG. 4A. As illustrated, theupper puck plate 415 has a first diameter that is larger than a seconddiameter of the lower puck plate 420. The backing plate 425 has a thirddiameter that is smaller than the second diameter of the lower puckplate 420. As mentioned previously with reference to FIG. 4A, thebacking plate 425 may have a smaller diameter than the lower puck plate420 to provide space for an RF gasket. Additionally, the lower puckplate 420 may include multiple inner features (not shown) and multipleouter features 498 that are to receive fasteners as described withreference to FIGS. 2-4A. The backing plate 425 may be sized such thatthe backing plate 425 does not block the outer features 498. The backingplate 425 may include holes 496 that provide access to the innerfeatures in the lower puck plate 420. As shown, the backing plate 425may include a center hole 492 to provide access to facilities.Additionally, the backing plate 425 includes three holes 494 around liftpin holes 499 in the lower puck plate 420.

FIG. 5A depicts a sectional side view of an electrostatic puck assembly510, in accordance with one embodiment. FIG. 5B depicts a perspectiveview the electrostatic puck assembly 510. Notably, the electrostaticpuck assembly 510 is shown upside down to better show particularcomponents of the electrostatic puck assembly 510. The electrostaticpuck assembly 510 is substantially similar to electrostatic puckassembly 410. For example, electrostatic puck assembly 510 includes anupper puck plate 515 bonded to a lower puck plate 520 by a metal bond555. The electrostatic puck assembly 510 further includes the lower puckplate 520 bonded to a backing plate 525 by another metal bond 565.Additionally, the backing plate 525 includes a center hole 592 toprovide access to facilities and further includes three holes 594 aroundlift pin holes 599 in the lower puck plate 520. The backing plate 525may additionally include holes 596 that provide access to the innerfeatures in the lower puck plate 520.

In electrostatic puck assembly 510, the backing plate 525 has a diameterthat is substantially similar to the diameter of the lower puck plate520. This further equalizes the forces applied to lower puck plate 520by upper puck plate 515 and backing plate 525. However, in such anembodiment there is no space to dispose an RF gasket that electricallyconnects the lower puck plate to a base plate. To provide an alternatepath for an RF signal, an outer sidewall of the backing plate 525 andthe metal bond 565 may be coated with an electrically conductive coating530. In one embodiment, the electrically conductive coating 530 is ametal coating such as an Aluminum coating. The electrically conductivecoating 530 may be applied using sputtering techniques, cold sprayingtechniques, or other metal deposition techniques. In one embodiment, theelectrically conductive coating 530 is covered by a plasma resistantceramic coating 535. The plasma resistant ceramic coating 535 may beY₂O₃ (yttria or yttrium oxide), Y₄Al₂O₉ (YAM), Al₂O₃ (alumina) Y₃Al₅O₁₂(YAG), YAlO₃ (YAP), Quartz, SiC (silicon carbide) Si₃N₄ (siliconnitride) Sialon, AlN (aluminum nitride), AlON (aluminum oxynitride),TiO₂ (titania), ZrO₂ (zirconia), TiC (titanium carbide), ZrC (zirconiumcarbide), TiN (titanium nitride), TiCN (titanium carbon nitride) Y₂O₃stabilized ZrO₂ (YSZ), and so on. The plasma resistant ceramic coating530 may also be a ceramic composite such as Y₃Al₅O₁₂ distributed inAl₂O₃ matrix, Y₂O₃—ZrO₂ solid solution or a SiC-Si₃N₄ solid solution. Inembodiments, the electrically conductive coating 530 and/or the plasmaresistant ceramic coating 535 may also coat an outer wall of the lowerpuck plate 520, metal bond 555 and/or upper puck plate 515. In oneembodiment, the electrically conductive coating 530 and the plasmaresistant ceramic coating 535 each have a thickness of about 5-25microns.

Since backing plate 525 has a diameter that is substantially similar tothe diameter of the lower puck plate 520, backing plate 525 coversfeatures (not shown) in the lower puck plate 520 that are configured toreceive fasteners. Accordingly, backing plate 525 may additionallyinclude holes 598 that provide access to the features in the lower puckplate 520.

In one embodiment, an electrical path for the RF signal may be providedby doping the backing plate 525 to increase an electrical conductivityof the backing plate 525. In one embodiment, Sm and/or Ce are used todope the backing plate 525. In one embodiment, the backing plate 525 hasan electrical resistivity of less than about 1×10⁹ Ohm centimeters (10E9Ohm·cm). In one embodiment, the backing plate has an electricalresistivity of about 10E6 Ohm·cm to 10E7 Ohm·cm. In such an embodiment,the outer wall of backing plate 525 may not be coated by theelectrically conductive coating 530. However, the outer wall of backingplate may still be coated with plasma resistant ceramic coating 535.

FIG. 6A depicts a sectional side view of an electrostatic puck assembly610, in accordance with one embodiment. FIG. 6B depicts a perspectiveview the electrostatic puck assembly 610. Notably, the electrostaticpuck assembly 610 is shown upside down to better show particularcomponents of the electrostatic puck assembly 610. The electrostaticpuck assembly 610 is substantially similar to electrostatic puckassembly 410. For example, electrostatic puck assembly 610 includes anupper puck plate 615 bonded to a lower puck plate 620 by a metal bond655. The electrostatic puck assembly 610 further includes the lower puckplate 620 bonded to a backing plate 670 by another metal bond 667. Thebacking plate 670 includes a center hole 692 to provide access tofacilities and further includes three holes 694 around lift pin holes699 in the lower puck plate 620. The backing plate 670 may additionallyinclude holes 696 that provide access to the inner features in the lowerpuck plate 620.

In electrostatic puck assembly 610, the backing plate 670 has a diameterthat is smaller than a diameter of the lower puck plate 620. In oneembodiment, backing plate 670 has a diameter that is approximately equalto the diameter of backing plate 425. Electrostatic puck assembly 610additionally includes a backing ring 660 that is metal bonded to lowerpuck plate 620 by metal bond 665. Backing ring 660 has an outer diameterthat is substantially similar to the diameter of the lower puck plate620. This further equalizes the forces applied to lower puck plate 620by upper puck plate 615 and a combination of the backing plate 670 andthe backing ring 660.

A space between the backing plate 670 and the backing ring 660 mayprovide room for an RF gasket that electrically connects the lower puckplate 620 to a base plate. Additionally, features 698 in the lower puckplate 620 that are configured to receive fasteners may be exposed. Inone embodiment, the outer walls of backing ring 660, metal bond 665,lower puck plate 620, metal bond 655 and/or upper puck plate 615 arecoated by a plasma resistant ceramic coating as described above withreference to FIGS. 5A-5B.

FIG. 7 illustrates one embodiment of a process 700 for manufacturing asubstrate support assembly. At block 704 of process 700, an upper puckplate is formed. The upper puck plate may be a ceramic disc thatincludes a clamping electrode and one or more heating elements.

At block 706, a lower puck plate is formed. In one embodiment, featuresare formed in a lower puck plate for receiving fasteners. Gas holes(e.g., He holes) may also be formed in the lower puck plate for flowinggases.

In one embodiment, at block 707 a metal protective coating is applied tothe lower puck plate. A metal protective coating may be applied to thelower puck plate, for example, if the lower puck plate is Molybdenum.The metal protective coating may be applied to ensure that the materialof the lower puck plate will not be exposed to plasma or processinggasses. The metal protective coating may have a thickness of about 2-10microns.

In one embodiment, the metal protective coating is Aluminum or anAluminum alloy such as Al 6061. In one embodiment, the metal protectivecoating is applied to the lower puck plate by electroplating. Theelectroplating may cause the metal protective coating to form over allsurfaces of the lower puck plate, including outer walls, a top andbottom, and inner walls of holes and features drilled in the lower puckplate. In another embodiment, the metal protective coating may beapplied by metal deposition techniques such as cold spraying orsputtering.

In one embodiment, metal protective plugs are inserted into holesdrilled in the lower puck plate instead of, or in addition to, applyingthe metal protective coating to the lower puck plate. For example,multiple counter-bored through holes may be drilled into the lower puckplate, and Aluminum (or Aluminum alloy) plugs may be inserted into theseholes. The plugs may protect a gas delivery area (e.g., the interior ofthe holes) from exposure to gases. The metal protective coating may ormay not then be applied over the lower puck plate.

In one embodiment, an outer wall of the lower puck plate is bead blastedto roughen the outer wall to a roughness (Ra) of about 100-200micro-inches. The outer wall may then be plasma sprayed with a plasmaresistant ceramic coating. The plasma resistant ceramic coating may beformed over the metal protective coating in embodiments. In oneembodiment, the plasma resistant ceramic coating has a thickness ofabout 2-10 microns. In a further embodiment, the plasma resistantceramic coating has a thickness of about 3 microns.

At block 708, a backing plate is formed. One or more holes may be formedin the backing plate (e.g., by drilling) to provide access to thefeatures and/or gas holes in the lower puck plate. In one embodiment, inwhich plugs are inserted into holes in the lower puck plate, gas groovesare formed in an upper side of the backing plate (where the backingplate will contact the lower puck plate). These gas grooves may provideaccess for gases to be flowed through the plugs, then through holes inthe upper puck plate. In one embodiment, the holes in the upper puckplate include a porous plug. Holes may also be drilled in the backingplate to provide a path for the gases to be flowed into the gas grooves.

At block 710, the lower puck plate is metal bonded to an upper puckplate using a first metal bond. At block 715, the backing plate is metalbonded to the lower puck plate using a second metal bond. A multilayerstack including the upper puck plate, the lower puck plate and thebacking plate may form an electrostatic puck assembly.

In one embodiment, the first metal bond is formed by placing a metalfoil of Al or AlSi alloy between the upper puck plate and the lower puckplate. In one embodiment, the second metal bond is formed by placing anadditional metal foil of Al or AlSi alloy between the lower puck plateand the backing plate. The metal foils may be approximately 50 micronsthick in one embodiment. Pressure and heat may be applied to form afirst diffusion bond between the metal foil, the upper puck plate andthe lower puck plate and to form a second diffusion bond between theadditional metal foil, the lower puck plate and the backing plate. Inone embodiment, a stack is formed that includes the upper puck plate,the metal foil, the lower puck plate, the additional metal foil and thebacking plate. This stack may then be hot pressed to form the firstmetal bond and the second metal bond in a single bonding process.

In one embodiment, at block 720 an electrically conductive coating isapplied to an outer wall of the backing plate. The electricallyconductive coating may also be applied over the metal bonds and/or overthe lower puck plate. The electrically conductive coating may be a metalcoating applied by cold spraying, sputtering, or other metal depositiontechnique. In one embodiment, at block 725 a plasma resistant ceramiccoating is applied over the electrically conductive coating. The plasmaresistant ceramic coating may be applied by plasma spraying, IAD, orother ceramic deposition technique.

At block 730, a thermal gasket is applied to a cooling plate. At block735, the cooling plate is secured to the electrostatic puck assembly. Inone embodiment, fasteners are inserted into the features in the lowerpuck plate and/or the cooling plate. In one embodiment, the fastenersare inserted into the lower puck plate prior to the lower puck platebeing bonded to the upper puck plate. In such an embodiment, thefasteners may be permanently embedded into the puck. The electrostaticpuck assembly may then be coupled to the cooling plate by tightening thefasteners (e.g., by threading bolts protruding from the features in thelower puck plate into nuts residing in the features in the coolingplate).

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent invention. It will be apparent to one skilled in the art,however, that at least some embodiments of the present invention may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentinvention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” When the term “about” or “approximately” is usedherein, this is intended to mean that the nominal value presented isprecise within ±10%.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. An electrostatic puck assembly comprising: anupper puck plate comprising AlN or Al₂O₃ and having a first coefficientof thermal expansion, the upper puck plate further comprising one ormore heating elements and one or more electrodes to electrostaticallysecure a substrate; a lower puck plate bonded to the upper puck plate bya first metal bond, the lower puck plate comprising material having asecond coefficient of thermal expansion that approximately matches thefirst coefficient of thermal expansion, the lower puck plate comprisinga plurality of features distributed over the lower puck plate at aplurality of different distances from a center of the lower puck plate,wherein each of the plurality of features accommodates one of aplurality of fasteners; and a backing plate bonded to the lower puckplate by a second metal bond, the backing plate comprising AlN or Al₂O₃,wherein the backing plate includes one or more holes that provide accessto at least some of the plurality of features of the lower puck platethrough the backing plate.
 2. The electrostatic puck assembly of claim1, wherein the upper puck plate has a first thickness of approximately3-10 mm, the backing plate has a second thickness of approximately 3-10mm, and the lower puck plate has a third thickness that is equal to orgreater than the first thickness and the second thickness.
 3. Theelectrostatic puck assembly of claim 2, wherein the first thickness isapproximately equal to the second thickness.
 4. The electrostatic puckassembly of claim 1, wherein the electrostatic puck assembly is operableat temperatures of up to 300° C. without damage to the electrostaticpuck assembly.
 5. The electrostatic puck assembly of claim 1, whereinthe lower puck plate has a first outer diameter that is approximatelyequal to a second outer diameter of the backing plate.
 6. Theelectrostatic puck assembly of claim 1, wherein the upper puck plate hasa first outer diameter that is greater than a second outer diameter ofat least one of the lower puck plate or the backing plate.
 7. Theelectrostatic puck assembly of claim 1, further comprising: acounter-bored through hole drilled in the lower puck plate; and a metalprotective plug inserted into the counter-bored through hole, whereinthe metal protective plug protects an interior of the counter-boredthrough hole from exposure to one or more gases.
 8. The electrostaticpuck assembly of the claim 1, wherein the lower puck plate comprises atleast one of a) Molybdenum, b) a metal matrix composite comprising Si,SiC and Ti, or c) a SiC porous body infiltrated with an AlSi alloy. 9.The electrostatic puck assembly of claim 1, further comprising: at leastone of a ring or a gasket disposed on a bottom of the electrostatic puckassembly, wherein at least one of the ring or the gasket is to becompressed via a force exerted by the plurality of fasteners, whereinthe plurality of fasteners are to each apply an approximately equalfastening force to couple a cooling plate to the electrostatic puckassembly, to compress at least one of the ring or the gasket, and tomaintain an approximately equal separation between the cooling plate andthe lower puck plate and facilitate a uniform heat transfer between thecooling plate and the lower puck plate.
 10. The electrostatic puckassembly of claim 9, wherein at least one of the ring or the gasketcomprises polyimide.
 11. The electrostatic puck assembly of claim 9,further comprising: the gasket; and a flexible graphite layer on thegasket.
 12. The electrostatic puck assembly of claim 9, furthercomprising: the cooling plate, coupled to the backing plate; and thegasket, wherein the gasket acts as a thermal choke between the coolingplate and the backing plate.
 13. A substrate support assemblycomprising: a multi-layer stack comprising: an electrically insulativeupper puck plate comprising one or more heating elements and one or moreelectrodes to electrostatically secure a substrate; and a lower puckplate bonded to the upper puck plate by a first metal bond, the lowerpuck plate comprising a plurality of features distributed over a bottomside of the lower puck plate at a plurality of different distances froma center of the lower puck plate, wherein each of the plurality offeatures accommodates one of a plurality of fasteners; and a base platecoupled to the multi-layer stack by the plurality of fasteners, whereinthe plurality of fasteners each apply an approximately equal fasteningforce to couple the base plate to the multi-layer stack, wherein theapproximately equal fastening force is to facilitate uniform heattransfer between a cooling plate and the multi-layer stack; and at leastone of a ring or a gasket compressed between the multi-layer stack andat least one of the base plate or the cooling plate.
 14. The substratesupport assembly of claim 13, the multi-layer stack further comprising:an electrically insulative backing plate bonded to the lower puck plateby a second metal bond, wherein the electrically insulative backingplate includes one or more holes that provide access to at least some ofthe plurality of features of the lower puck plate through the backingplate.
 15. The substrate support assembly of claim 14, wherein the upperpuck plate comprises AlN or Al₂O₃, the backing plate comprises AlN orAl₂O₃, and the lower puck plate comprises one of a) Molybdenum, b) ametal matrix composite comprising Si, SiC and Ti, or c) a SiC porousbody infiltrated with an AlSi alloy.
 16. The substrate support assemblyof claim 13, wherein at least one of the ring or the gasket comprisespolyimide.
 17. The substrate support assembly of claim 13, wherein thecooling plate is connected to the base plate by a plurality of springs,wherein the plurality of springs apply a force to press the coolingplate against the multi-layer stack.
 18. The substrate support assemblyof claim 17, further comprising: the gasket, disposed between themulti-layer stack and the cooling plate, wherein the plurality ofsprings compress the gasket, and wherein the gasket acts as a thermalchoke between the cooling plate and the multi-layer stack.
 19. Thesubstrate support assembly of claim 18, further comprising: a flexiblegraphite layer on the gasket.
 20. The substrate support assembly ofclaim 13, further comprising: the ring, wherein the ring is an O-ringcompressed between the electrically insulative upper puck plate and thebase plate.